Question

我们的系统正在接收来自两个外部来源的输入（电话/网络提交）。

//  Table-Per-Type Hierarchy
public class Submission
{
    public int SubmissionId { get; set; }   // Primary Key
    public int? PersonId { get; set; }
    public int? CompanyId { get; set; }
    public long? EmployeeId { get; set; }
    public bool? Completed { get; set; }
    public string AbsenceReason { get; set; }
    public string AbsenceType { get; set; }
    public DateTime? AbsenceDate { get; set; }
}

public class CallSubmission : Submission
{
    public string CallerId { get; set; }
    public string PhoneNumber { get; set; }
    public DateTime? HangUp { get; set; }
    public DateTime? PickUp { get; set; }        
}

public class WebSubmission : Submission
{
    public string EmailAddress { get; set; }
    public string PhoneNumber { get; set; }
    public DateTime SubmissionDate { get; set; }
}

我的目标是使用 PickUp / SubmissionDate 检索过去七天内的所有提交内容，具体取决于我们正在处理的提交类型。是否可以使用单个LINQ语句实现此目的？理想情况下，我希望避免在内存中加载两个不同的数据集。

我希望整合的声明

Users.Where(user => user.UserName == name)
     .SelectMany(user => user.Submissions)
     .OfType<CallSubmission)()
     .Where(call => call.PickUp >= startDate)

Users.Where(user => user.UserName == name)
     .SelectMany(user => user.Submissions)
     .OfType<WebSubmission>()
     .Where(web => web.SubmissionDate >= startDate)

Answer 1

实际上（令我惊讶的是）你问的是什么（至少在最新的EF6.1.3中），因为支持C＃is和as运算符（它们基本上被{{{ 1}}方法）。

OfType

重要的一部分是使用var query = db.Users .Where(user => user.UserName == name) .SelectMany(user => user.Submissions) .Where(subm => (subm as CallSubmission).PickUp >= startDate || (subm as WebSubmission).SubmissionDate >= startDate);运算符而非as生成不受支持的异常。无需检查cast，因为生成的SQL查询自然会处理null。

实体框架 - 使用TPT设置加载子类实体

1 个答案: